Determining Whether Copies are from a Common Source

There are a variety of defects that may appear on copies due to:
• Excessive toner or extraneous toner being deposited on the resultant copies which is often associated with the cleanliness and service record of the machine
• Marks on the photocopy glass, mirrors etc.
• Marks deposited by rollers and guiding mechanisms
• Marks produced by a machine's "finger pickers" which assist in separating documents and guiding documents through the mechanism

These can be highly individualistic and may be either permanent or transitory in nature. The observation of matching defects, especially extraneous toner marks, can result in a firm opinion being offered that documents have originated from a single copier.
The changing nature of these defects when observed relative to a selection of documents of known date and from the same machine may also assist in identifying the true date of production of a particular copy document.

Manipulation of Copy Documents

When a copy document is presented for examination, it does not necessarily follow that an original document, in the same format, bearing a pen and ink signature, was ever in existence. It has to be appreciated that it is a relatively simple task to transpose a genuine signature from one document onto another. Examinations can be undertaken to determine whether a signature transposition may have occurred.

A questioned document can be examined to determine whether textual entries have been manipulated, for example, to consider whether the questioned document, as presented, is actually a montage document.